X-ray diffraction study on precipitate of Er:LiNbO3 induced by vapor transport equilibration |
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Authors: | D Zhang G Lan X Chen D Zhu |
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Institution: | (1) Department of Opto-electronics and Information Engineering, College of Precision Instruments and Opto-electronics Engineering, Tianjin University, Tianjin 300072, P.R. China, CN;(2) Department of Physics, Nankai University, Tianjin 300071, P.R. China, CN |
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Abstract: | An X-ray powder diffraction study was performed on vapor transport equilibration (VTE) treated Er:LiNbO3 crystals with different doping levels (0.2, 0.4 and 2.0% Er per cation site), different cut orientations (X- and Z-cuts)
and different VTE durations (120, 150 and 180 h). Their diffraction characteristics were compared with those of pure congruent
LiNbO3 and as-grown Er:LiNbO3. The most significant characteristic is the appearance of additional weak and broad peaks around the 2θ angles 30° and 59°
in the diffraction patterns of both X- and Z-cut 2.0 mol% doped VTE crystals, confirming that they precipitated. A further
comparison of their diffraction data with the powder diffraction files indicated that the new phase in these precipitated
crystals is ErNbO4, which has an approximate concentration of 1.0%, 1.065%, 1.485% for 120, 150 and 180 h crystals, respectively. The crystalline
grain sizes of the new phase are 132.2∼184.1?. The unit cell parameters of the as-grown and VTE crystals were also determined
from diffraction data; the variation from pure LiNbO3 to as-grown Er:LiNbO3 was qualitatively explained according to the crystal structure of LiNbO3 and using the concept of ionic radius. VTE brings the crystal closer to a stoichiometric composition, thus causing the contraction
of the lattice constants. Finally, a tentatively qualitative explanation for precipitate formation is given on the basis of
crystal structure.
Received: 2 August 2000 / Accepted: 29 March 2001 / Published online: 20 June 2001 |
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Keywords: | PACS: 81 05 -t 81 20 -n 82 30 -l 61 10 -n |
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